HTML The Definitive Guide (79 page)
Read HTML The Definitive Guide Online
Authors: Chuck Musciano Bill Kennedy
7.6.1.5 Server dependencies
Like image maps, searchable documents require support from the server to make things work. How the server interprets the query URL and its parameters is not defined by the HTML standard.
You should consult your server's documentation to determine how you can receive and use the search parameters to locate the desired document. Typically, the server breaks the parameters out of the query URL and passes them to a program designated by the URL.
7.5 Mouse-Sensitive Images
7.7 Establishing Document
Relationships
7.7 Establishing Document Relationships
Very few HTML documents stand alone. Instead, a document is usually part of a collection of documents, each connected by the one or several of the hypertext strands we describe in this chapter.
One document may be a part of several collections, linking to some documents and being linked to by others. Readers move between the document families as they follow the links that interest them.
You establish an explicit relationship between two documents when you link them. Conscientious authors use the rel attribute of the tag to indicate the nature of the link. In addition, two other tags may be used within a document to further clarify the location and relationship of a document within a document family. These tags,
tag. [, 3.6]
7.7.1 The
As we previously explained, URLs within a document can be either absolute (with every element of the URL explicitly provided by the author) or relative (with certain elements of the URL omitted and supplied by the browser). Normally, the browser fills in the blanks of a relative URL by drawing the missing pieces from the URL of the current document. You can change that with the
Function:
Define the base URL for other anchors in the document Attributes:
HREF
TARGET
End tag:
None
Contains:
Nothing
Used in:
head_content
The , , and
7.7.1.1 The href attribute
The href attribute must have a valid URL as its value, which the browser then uses to define the absolute URL against which relative URLs are based within the document. For example, the
...
tells the browser that any relative URLs within this document are relative to the top-level document directory on
www.kumquat.com
, regardless of the address and directory of the machine from which the user had retrieved the current document.
Contrary to what you may expect, you can make the base URL relative, not absolute. The browser actually forms an absolute base URL out of this relative URL by filling in the missing pieces with the URL of the document itself. This property can be used to good advantage. For instance, in this next example:
...
the browser will make the
info
directory, which probably is not the same directory of the current document. Imagine if you had to re-address every link in your document with that common directory. Not only does the
7.7.1.2 The target attribute
When working with documents inside frames, the target attribute with the tag ensures that a referenced URL gets loaded into the correct frame. Similarly, the target attribute for the
display redirected hyperlinked documents. [An Overview of Frames, 12.1]
If you have no other default target for your hyperlinks within your frames, you may want to consider using
7.7.1.3 Using
The most important reason for using
You also need to use the
Note that a document that contains both the
7.7.2 The Header Element
Use the tag to define the relationship between the current document and another in a Web collection.
Function:
Define a relationship between this document and another document Attributes:
CHARSET ONKEYUP
CLASS ONMOUSEDOWN
DIR ONMOUSEMOVE
HREF ONMOUSEOUT
HREFLANG ONMOUSEOVER
ID ONMOUSEUP
LANG REL
MEDIA REV
ONCLICK STYLE
ONDBLCLICK TARGET
ONKEYDOWN TITLE
ONKEYPRESS TYPE
End tag:
None
Contains:
Nothing
Used in:
head_content
The tags belongs in the
content, nowhere else. The attributes of the tag are used like those of the tag, but their effects serve only to document the relationship between documents. The tag has no content and no closing element.7.7.2.1 The href attribute
As with its other tag applications, the href attribute specifies the URL of the target tag. It is a required attribute, too, and its value is any valid document URL. The specified document is assumed to have a relationship to the current document.
7.7.2.2 The rel and rev attributes
The rel and rev attributes express the relationship between the source and target documents. The rel attribute specifies the relationship from the source document to the target; the rev attribute specifies the relationship from the target document to the source document. Both attributes can be included in a single tag.
The value of either attribute is a space-separated list of relationships. The actual relationship names are not specified by the HTML standard, although some have come into common usage as listed in section
Section 7.3.1.5, "The rel and rev attributes"
. For example, a document that is part of a sequence of documents might use: when referencing the next document in the series. The relationship from the source to the target is that of moving to the next document; the reverse relationship is that of moving to the previous document.
7.7.2.3 The title attribute
The title attribute lets you specify the title of the document to which you are linking. This attribute is useful when referencing a resource that does not have a title, such as an image or a non-HTML
